private Actor getNearestObject()
{
    int diff = 1000000; Actor nearest = null;
    for (Actor a : getWorld().getObjects(ClassName.class))
    {
        int d = diff = (int) Math.sqrt(Math.pow(getX()-a.getX(),2)+Math.pow(getY()-a.getY(),2));
        if (d < diff)
        {
            diff = d;
            nearest = a;
        }
    }
    return nearest;
}

public Minnow nearestMinnow()
    {
        int diff = 1000000; 
        Actor nearest = null;
        for (Actor minnow : getWorld().getObjects(Minnow.class))
        {
            int d = diff = (int) distanceTo(minnow);
            if (d < diff)
            {
                diff = d;
                nearest = minnow;
            }
        }
            return nearest;
    }

int d = (int) distanceTo(minnow);

public void testNearestMinnow2()
    {
        Minnow dory = new Minnow();
        Minnow nemo = new Minnow();
        ocean.add(dory, 50, 51);
        ocean.add(shark, 50, 50);
        ocean.add(nemo, 100, 100);

        assertEquals(dory, shark.nearestMinnow());
    }